Estes C6-3 Standard Engines18mm-PO 1613 The Estes C6-3 engine is a single stage engine designed for model rocket flight. This engine is a standard engine designed for flights in rockets weighing less than 4 ounces, including the engine. Each package includes 3 engines, 4 starters and 4 plugs. Originally: Sale Price: $12.99 Add to Cart